Semiconductor integrated circuit device

ABSTRACT

A finger length a 1  of a transistor P 11  is longer than a finger length A 1  of a transistor P 1 , and a finger length b 1  of a transistor N 11  is longer than a finger length B 1  of a transistor N 1 . The finger length b 1  of the transistor N 11  is shorter than the finger length A 1  of the transistor P 1 , and the relation: a 1 &gt;A 1 &gt;b 1 &gt;B 1  is established. In a relation between an I/O section and a logic circuit section, as for MOS transistor of the same conductive type, a finger length of a MOS transistor constituting the logic circuit section is set so as to be longer than a finger length of a MOS transistor constituting the I/O section.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor integrated circuitdevice, and particularly relates to a semiconductor integrated circuitdevice provided on an SOI substrate.

2. Description of the Background Art

In a current semiconductor integrated circuit device (LSI) having aplurality of circuit sections with different functions, such as aninput/output circuit (I/O) section, a logic circuit section and a memorysection, a configuration is adopted where a plurality of voltages aresupplied from external power supplies.

For example, an LSI with two power supplies has been used in relativelymany practical uses, in which a 3.3 V power supply is used for theinput/output circuit section and a 1.2 V power supply is used for a corecircuit section corresponding to core portions of the LSI such as thelogic circuit section and the memory circuit section.

Here, a structure (a gate length and a thickness of a gate insulatingfilm) of a MOS transistor included in each of the circuit sections thatconstitute the LSI differs depending upon a power voltage, and a channelwidth of the MOS transistor also differs depending upon the circuitsection.

For example, in the MOS transistor in the input/output circuit sectionusing the 3.3 V power supply, the channel width is set to not less than100 μm. This is because, as disclosed in Japanese Patent ApplicationLaid-Open No. 2000-349165 (FIG. 3), the MOS transistor in theinput/output circuit section is required to have excellent noiseresistance.

On the other hand, in the core circuit section such as the logic circuitsection and the memory circuit section, the channel width is set to theorder of several μm for the purpose of improving a package density.

As thus described, the input/output circuit section and the circuitsection are significantly different in MOS transistor structure. Inparticular, the MOS transistor constituting the input/output circuitsection has been required to have a long channel width. However, inorder to respond to such a requirement by only one gate electrode, alength of the gate electrode in the channel width direction wouldnaturally become not less than 100 μm.

Here, the input/output circuit section is provided along the end edge ofthe LSI due to the nature of its function. The shape of the providedregion in a plan view is often slim rectangular, and the length of thegate electrode of the MOS transistor in the channel width directioncannot be made longer without restriction.

Therefore, a configuration has been adopted where a plurality of gateelectrodes having the same length are provided in parallel and aplurality of MOS transistors are connected in parallel in place of oneMOS transistor having one long gate electrode.

In this case, a total of lengths (referred to as finger lengths) of aportion on an active region (here, SOI layer) of each of the gateelectrodes is a channel width. The finger lengths of the plurality ofgate electrodes are set so as to correspond to a channel width of oneMOS transistor having one long gate electrode.

For example, in a case where a MOS transistor having a channel width of100 μm is required, restriction on area has been avoided by aligning twoMOS transistors in parallel each having a finger length of 50 μm oraligning four MOS transistors in parallel each having a finger length of25 μm.

As thus described in the input/output circuit section of theconventional LSI, the structure of the MOS transistor was determinedonly on ground of restriction on area, and this is because a bulkdevice, which is a semiconductor device formed directly on a siliconsubstrate called bulk substrate, was a subject to be obtained. On an SOIdevice which is currently mainstream, there are restrictions asdescribed below.

Namely, a semiconductor device formed on an SOI (silicon on insulator)substrate, so-called SOI device, which is provided sequentially with aburied oxide film and an SOI film has a characteristic of being capableof reducing a parasitic capacitance so as to perform a stable operationat high speed with low power consumption, and has been in use for mobiledevices.

One of examples of the SOI device is an SOI device with a full trenchseparation (FTI) structure where elements are electrically isolated by afull trench isolation insulating film formed by providing a trenchreaching the buried oxide film within the surface of the SOI layer andthen burying an insulator into the trench.

However, there have been a variety of problems generated by a substratefloatation effect, including a problem in that carriers (holes in NMOS)generated by a collisional ionization phenomenon remain in a body regionincluding a channel formation region, thereby to cause generation of akink, reduction in operating withstand voltage, and generation ofdependency of delayed time on a frequency due to an unstable potentialof the body region.

With this being the situation, a partial trench isolation (PTI)structure was contrived as disclosed in Japanese Patent ApplicationLaid-Open No. 2000-243973 (FIGS. 1 to 3). This structure has a partialtrench isolation insulating film formed by forming a trench within thesurface of the SOI layer such that the SOI layer with a prescribedthickness remains between the bottom of the trench and a buried oxidefilm and then burying an insulator into the trench.

Adoption of the PTI structure allows shift of carriers through a wellregion in the lower portion of the partial trench isolation insulatingfilm so as to prevent the carriers from remaining in the body region,and also allows fixing of a potential of the body region through thewell region. Accordingly, the variety of problems caused by thesubstrate floatation effect are not generated.

In the case of adopting the PTI structure, typically, a high densityimpurity region of the same conductivity type as that of the body regionis provided as a body contact region within the surface of the SOI layeron the outside of the end of the gate electrode in the gate widthdirection, and the body contact region is electrically connected to awiring layer as an upper layer, to fix a potential of the body region.

However, in the case of adopting the PTI structure, when the channelwidth of the MOS transistor is increased without restriction, the bodyregion under the gate electrode becomes longer, resulting in that bodyresistance increases to make it difficult to fix a potential of the bodyregion, leading to a problem of deterioration in transistorcharacteristic caused by the substrate floatation effect.

As thus described, there has been a problem in the SOI device with theSOI structure adopted therein in that the length of the MOS transistorin the channel width direction cannot be increased from the aspect ofsuppressing deterioration in transistor characteristic, and it has notbeen possible to solve the problem by a conventional design index ofarranging gate electrodes in parallel to avoid restriction on area.

SUMMARY OF THE INVENTION

There is provided a semiconductor integrated circuit device, which isprovided on an SOI substrate and includes an input/output circuitsection and a core circuit section and in which a power-supply voltageof the input/output circuit section is higher than a power-supplyvoltage of the core circuit section, wherein deterioration incharacteristic caused by a substrate flotation effect of a MOStransistor constituting the input/output circuit section can beprevented.

A first mode of the semiconductor integrated circuit device according tothe present invention is provided on an SOI substrate and includes: aninput/output circuit section; and a core circuit section, which isprovided more internally than the input/output circuit section andoperate at a lower power supply voltage than the input/output circuitsection. The input/output circuit section has a first MOS transistor ofa first conductivity type. The core circuit section has a second MOStransistor of the first conductivity type. A first finger length of afirst gate electrode of the first MOS transistor, which is defined by alength of a portion on an active region, is set shorter than a secondfinger length of a second gate electrode of the second MOS transistor,which is defined by a length of a portion on an active region.

As thus described, in an input/output circuit section, a first fingerlength of a first gate electrode of a first MOS transistor, which isdefined by a length of a portion on an active region, is set shorterthan a second finger length of a second gate electrode of the second MOStransistor, which is defined by a length of a portion on an activeregion. Therefore, ever when a collisional ionization phenomenonapparently occurs at a drain end of the MOS transistor, it is possiblein the input/output circuit section to which a higher power supplyvoltage is supplied than the core circuit section to suppress asubstrate floatation effect with reliability, so as to preventdeterioration in transistor characteristic caused by the substratefloatation effect.

A second mode of the semiconductor integrated circuit device accordingto the present invention is provided on an SOI substrate and includes:an input/output circuit section; and a core circuit section, which isarranged more internally than the input/output circuit section andoperates at a lower power-supply voltage than the input/output circuitsection. The input/output circuit section has a plurality of kinds ofMOS transistors in a first group. The core circuit section has aplurality of kinds of MOS transistors in a second group. A finger lengthof each of gate electrodes of the plurality of kinds of MOS transistorsin the first group in the input/output circuit section is different, thelength being defined by a length of a portion on an active region. Afinger length of each of gate electrodes of the plurality of kinds ofMOS transistors in the second group in the core circuit section isdifferent, the length being defined by a length of a portion on anactive region. The maximum finger length among the respective fingerlengths of the plurality of kinds of MOS transistors in the first groupis shorter than the maximum finger length among the respective fingerlengths of the plurality of kinds of MOS transistors in the secondgroup.

As thus described, in an input/output circuit section, the maximumfinger length among respective finger lengths of a plurality of kinds ofMOS transistors in a first group is set shorter than the maximum fingerlength among respective finger lengths of a plurality of kinds of MOStransistors in a second group. Therefore, in a case where a plurality ofkinds of MOS transistor having different finger lengths are providedwithin the same one circuit, even when a collisional ionizationphenomenon apparently occurs at a drain end of the MOS transistors, itis possible in the input/output circuit section to which a higher powersupply voltage is supplied than the core circuit section to suppress asubstrate floatation effect with reliability, so as to preventdeterioration in transistor characteristic caused by the substratefloatation effect.

These and other objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view for explaining fixing of a potential of a bodyregion in an SOI device with a PTI structure adopted therein;

FIG. 2 is a sectional view for explaining fixing of a potential of thebody region in the SOI device with the PTI structure adopted therein;

FIG. 3 is a block diagram showing one of examples of a wholeconfiguration of a semiconductor integrated circuit device to which thepresent invention is applied;

FIG. 4 is a plan view for explaining a first constitutional example ofthe semiconductor integrated circuit device according to the presentinvention;

FIG. 5 is a plan view for explaining a second constitutional example ofthe semiconductor integrated circuit device according to the presentinvention;

FIG. 6 is a plan view for explaining a third constitutional example ofthe semiconductor integrated circuit device according to the presentinvention; and

FIG. 7 is a semiconductor integrated circuit device provided on an SOIsubstrate whose crystal plane orientation has been partially changed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment A. Regarding Fixingof Potential of Body Region

First, fixing of a potential of a body region in an SOI device with thePTI structure adopted therein is described using FIGS. 1 and 2.

FIG. 1 is a view showing a plane configuration of a a MOS transistor(NMOS transistor) N10 with the PTI structure adopted therein. FIG. 2 isa sectional view on arrow A-A of FIG. 1. In FIG. 1, two gate electrodesGT are provided in parallel in a gate length direction on an SOIsubstrate SB. A drain region DR in which P-type impurities have beenintroduced is provided between the two gate electrodes GT within thesurface of the SOI substrate SB. The source region SR in which theP-type impurities have been introduced is provided on the outside sidesurface of the gate electrode GT on the opposite side to the drainregion DR within the surface of the SOI substrate SB.

A body contact region BC is provided on the outside of one end of thetwo gate electrodes GT in a gate width direction, in a position apartfrom an active region including the drain region DR and the sourceregion SR.

The body contact region BC is an impurity region for fixing a potentialof a body region corresponding to the SOI layer region immediately underthe gate electrode GT. A partial trench isolation insulating film PT isprovided between the body contact region BC and the active region.

It is to be noted that the drain region DR, the source region SR and thebody contact region BC are connected to wiring (not shown) in an upperlayer through a contact portion CH. And the other ends of gateelectrodes GT in the gate width direction are connected so as to be acommon gate electrode, and is connected to wiring (not shown) in anupper layer through a contact portion CH.

Further, as shown in FIG. 2, the SOI substrate SB has a configurationwhere an oxide film 2 and an SOI layer 3 are sequentially provided on asubstrate 1, and a gate insulating film GX is provided between the gateelectrode GT and the SOI layer 3.

Moreover, a configuration is made such that an interlayer insulatingfilm 4 is provided so as to cover the SOI substrate SB including thegate electrode GT, and the wiring layer WR is provided on the interlayerinsulating film 4 to be connected to the contact portion CH.

Subsequently, the structure is made such that a full trench isolationinsulating film having such a thickness as to reach the buried oxidefilm 2 is provided so as to define the active region including the drainregion DR and the source region SR, and thereby, elements are fullyisolated electrically.

The partial trench isolation insulating film PT, formed such that theSOI layer 3 remains between the bottom and the oxide film, is providedbetween the body contact region BC and the active region, and the bodycontact region BC is electrically connected to the body region throughthe SOI layer 3 (well region) under the partial trench isolationinsulating film PT.

It is to be noted that the NMOS transistor N10 has a configurationcomprising the body contact region capable of fixing a potential of thebody region to the outside of one end out of both ends of the bodyregion in the gate width direction. As thus described, the configurationcomprising the body contact region on the outside of one end of the bodyregion in the gate width direction is called one-side potential fixing.

With this configuration, it is possible to shift carriers through thewell region under the partial trench isolation insulating film, and thusprevent the carriers from remaining in the body region and fix apotential of the body region through the well region, so as to prevent avariety of kinds of problems caused by the substrate floatation effect.

However, since resistance of the body region under the gate electrode GTin the SOI device is higher than in the bulk device, the finger lengthin the SOI device is made shorter than in the bulk device.

Further, as a power-supply voltage becomes higher, a collisionalionization phenomenon at the drain end occurs more apparently, wherebythe substrate floatation effect occurs more apparently. Therefore, thefinger length of the MOS transistor in the input/output circuit sectionat a higher power supply voltage is made shorter than in the corecircuit section at a lower power-supply voltage. This is a basictechnical idea of the present invention.

First, one of examples of the whole configuration of the semiconductorintegrated circuit device to which the present invention is applied isdescribed using a block diagram shown in FIG. 3.

A semiconductor integrated circuit device 100 shown in FIG. 3 includesan input/output (I/O) circuit section 101, a logic circuit section 102,a memory section 103, an analog section 104, and a computing section105. The I/O section 101 is provided along four sides of thesemiconductor integrated circuit device 100. The circuit sections exceptfor the input/output I/O section 101 are a so-called core circuitsection. A 3.3 V power supply is used for the input/output circuitsection, and a 1.2 V power supply is used for the core circuit section.

It should be noted that the above configuration is one of examples, andapplication of the present invention is not limited to this. The presentinvention is applicable to any semiconductor integrated circuit deviceso long as the device has an input/output circuit section and a corecircuit section.

B. First Constitutional Example of Device

Next, a first constitutional example of the I/O section 101 and thelogic circuit section 102 is described using FIG. 4 that shows a detailof a region X across the I/O section 101 and the logic circuit section102 in FIG. 3.

B-1. Configuration of I/O Section

In FIG. 4, the I/O section 101 is provided with: a transistor columnwhere a P-channel type MOS transistor (PMOS transistor) P1 and anN-channel type MOS transistor (NMOS transistor) N1 are provided inparallel in the gate width direction, and the gate electrodes G1 of bothtransistors are connected so as to be a common gate electrode; and atransistor column where a PMOS transistor P2 and an NMOS transistor N2are provided in parallel in the gate width direction, and the gateelectrodes G1 of both transistors are connected so as to be a commongate electrode.

Here, the PMOS transistor P1 and the NMOS transistor N1 have two gateelectrodes G1 provided in parallel in the gate length direction. In thePMOS transistor P1, a drain region 23 in which P-type impurities havebeen introduced is provided between the gate electrodes G1 within thesurface of the SOI substrate SB, and a source region 22 in which P-typeimpurities have been introduced is provided between the gate electrodesG1 on the outside of the side surface of each of the gate electrodes G1on the opposite side to the drain region 23 within the surface of theSOI substrate SB. Therefore, the PMOS transistor P1 has a configurationwhere two PMOS transistors are connected in parallel, but those aretreated as one transistor for the sake of convenience.

Similarly, in the NMOS transistor N1, a drain region 13 in which N-typeimpurities have been introduced is provided between the gate electrodesG1 within the surface of the SOI substrate SB, and a source region 12 inwhich N-type impurities have been introduced is provided between thegate electrodes G1 on the outside of the side surface of each of thegate electrodes G1 on the opposite side to the drain region 13 withinthe surface of the SOI substrate SB. Therefore, the NMOS transistor N1has a configuration where two NMOS transistors are connected inparallel, but those are treated as one transistor for the sake ofconvenience.

The periphery of the active region of each of the PMOS transistor P1 andthe NMOS transistor N1 is surrounded by the partial trench isolationinsulating film PT, and body contact regions 24 and 14 are provided onthe outside of both ends of the two gate electrodes G1 in the gate widthdirection, in positions apart from the respective active regions. Itshould be noted that the full trench isolation insulating film is formedoutside the partial trench isolation insulating film PT within thesurface of the SOI substrate SB.

Both the body contact regions 24 and 14 are provided continuously alongthe arrangement direction of the two gate electrodes G1. It is to benoted that each of the body contact regions 24 and 14 is provided on aboundary portion between the partial trench isolation insulating film PTand the full trench isolation insulating film.

Adoption of such a configuration allows fixing of a potential of eachend of the body region in the gate width direction in each of the PMOStransistor P1 and the NMOS transistor N1, so as to make body resistanceof the body region substantially half as large as in the case of theone-side potential fixing. As thus described, a configuration comprisinga body contact region capable of fixing a potential of a body region onthe outside of each end of the body region in the gate width directionis called both-side potential fixing.

Further, each of the PMOS transistor P2 and the NMOS transistor N2 hasfour gate electrodes G1 provided in parallel in the gate lengthdirection, and the PMOS transistor P2 has a configuration where fourPMOS transistors are connected in parallel, but those are treated as onetransistor for the sake of convenience. It should be noted that thebasic transistor structure is the same as that of the PMOS transistor P1and its description is thus omitted.

Similarly, the NMOS transistor N2 has a configuration where four NMOStransistors are connected in parallel, but those are treated as onetransistor for the sake of convenience. It should be noted that thebasic transistor structure is the same as that of the NMOS transistor N1and its description is thus omitted.

B-2. Configuration of Logic Circuit Section

Further, the logic circuit section 102 is provided with: a transistorcolumn where a PMOS transistor P11 and an NMOS transistor N11 areprovided in parallel in the gate width direction, and the gateelectrodes G11 of both transistors are connected so as to be a commongate electrode; and a transistor column where a PMOS transistor P12 andan NMOS transistor N12 are provided in parallel in the gate widthdirection, and the gate electrodes G11 of both transistors are connectedso as to be a common gate electrode.

Here, the number of gate electrodes G11 in common between the PMOStransistor P11 and the NMOS transistor N11 is one, and in the PMOStransistor P11, a source region 42 and a drain region 43 in which theP-type impurities have been introduced are provided on the outside ofboth side surfaces of the gate electrode G11 in the gate lengthdirection within the surface of the SOI substrate SB.

Similarly, in the NMOS transistor Nil, a source region 32 and a drainregion 33 in which the N-type impurities have been introduced areprovided on the outside of both side surfaces of the NMOS transistor N11in the gate length direction within the surface of the SOI substrate SB.

The periphery of the active region of each of the PMOS transistor P11and the NMOS transistor N11 is surrounded by the partial trenchisolation insulating film PT, and body contact regions 44 and 34 areprovided on the outside of both ends of the two gate electrodes G11 inthe gate width direction, in positions apart from the respective activeregions. It should be noted that the full trench isolation insulatingfilm is formed outside the partial trench isolation insulating film PTwithin the surface of the SOI substrate SB.

In addition, each of the body contact regions 44 and 34 is provided on aboundary portion between the partial trench isolation insulating film PTand the full trench isolation insulating film

Adoption of such a configuration allows fixing of a potential of eachend of the body region in the gate width direction in each of the PMOStransistor P11 and the NMOS transistor N11, so as to make bodyresistance of the body region substantially half as large as in the caseof the one-side potential fixing.

Further, each of the PMOS transistor P12 and the NMOS transistor N12 hastwo gate electrodes G11 provided in parallel in the gate lengthdirection. In the PMOS transistor P12, the drain region 43 in which theP-type impurities have been introduced is provided between the gateelectrodes G11 within the surface of the SOI substrate SB. And a sourceregion 42 in which P-type impurities have been introduced is providedbetween the gate electrodes G11 on the outside of the side surface ofeach of the gate electrodes G11 on the opposite side to the drain region43 within the surface of the SOI substrate SB. Therefore, the PMOStransistor P12 has a configuration where two PMOS transistors areconnected in parallel, but those are treated as one transistor for thesake of convenience.

Similarly, in the NMOS transistor N12, the drain region 33 in which theN-type impurities have been introduced is provided between the gateelectrodes G11 within the surface of the SOI substrate SB, and a sourceregion 32 in which N-type impurities have been introduced is providedbetween the gate electrodes G11 on the outside of the side surface ofeach of the gate electrodes G11 on the opposite side to the drain region33 within the surface of the SOI substrate SB. Therefore, the NMOStransistor N12 has a configuration where two NMOS transistors areconnected in parallel, but those are treated as one transistor for thesake of convenience.

The periphery of the active region of each of the PMOS transistor P12and the NMOS transistor N12 is surrounded by the partial trenchisolation insulating film PT, and body contact regions 44 and 34 areprovided on the outside of both ends of the two gate electrodes G11 inthe gate width direction, in positions apart from the respective activeregions. It should be noted that the full trench isolation insulatingfilm is formed outside the partial trench isolation insulating film PTwithin the surface of the SOI substrate SB.

Both of the body contact regions 44 and 34 are provided continuouslyalong the arrangement direction of the two gate electrodes G11. It is tobe noted that each of the body contact regions 44 and 34 is provided ona boundary portion between the partial trench isolation insulating filmPT and the full trench isolation insulating film.

In addition, it goes without describing that the both-side potentialfixing is also adopted in the PMOS transistor P12 and the NMOStransistor N12.

B-3. Comparison Between I/O Section and Logic Circuit Section

Next, MOS transistors constituting the I/O section 101 and the logiccircuit section 102 is subjected to comparison with reference to FIG. 4.

First, a focus is placed on the transistor column consisting of the PMOStransistor P1 and the NMOS transistor N1 in the I/O section 101. Thistransistor column is configured such that a finger length (length of aportion on the active region of the gate electrode) A1 of the gateelectrode G1 of the PMOS transistor P1 is made about twice as long as afinger length B1 of the gate electrode G1 of the NMOS transistor N1.This also applies to the PMOS transistor P2 and the NMOS transistor N2.

Here, in the PMOS transistor P2 and the NMOS transistor N2, since foureach of PMOS transistors and NMOS transistors are connected in parallel,respective total finger lengths of the PMOS transistor P2 and the NMOStransistor N2 are gate widths of the PMOS transistor P2 and the NMOStransistor N2, and are twice as wide as the gate widths of the PMOStransistor P1 and the NMOS transistor N1.

It should be noted that the reason for configuring the MOS transistorsuch that the finger length A1 of the gate electrode G1 of the PMOStransistor P1 (P2) is about twice as long as the finger length B1 of thegate electrode G1 of the NMOS transistor N1 (N2) is described below.

The following relation is established between the NMOS transistor andthe PMOS transistor. A current amount per unit channel width of the NMOStransistor is about twice as large as that of the PMOS transistor, andas for the maximum finger length with which the substrate floatationeffect can suppressed in each of the NMOS transistor and the PMOStransistor, about one-half of the maximum finger length of the PMOStransistor corresponds to the maximum finger length of the NMOStransistor N. This is not limited to the I/O section 101, but alsoapplies to the core circuit section.

Next, a focus is placed on the transistor column consisting of the PMOStransistor P 11 and the NMOS transistor N11 in the logic circuit section102. This transistor column is configured such that a finger length a1of the gate electrode GT of the PMOS transistor P 11 is made about twiceas long as a finger length b1 of the gate electrode G1 of the NMOStransistor N11. This also applies to the PMOS transistor P12 and theNMOS transistor N12.

Next, a focus is placed on the finger length of each of the PMOStransistor P1 and the NMOS transistor N1 in the I/O section 101 and thePMOS transistor P11 and the NMOS transistor N11 in the logic circuitsection 102, to find the magnitude relation of these finger lengths asfollows.

Namely, the finger length a1 of the PMOS transistor P11 is longer thanthe finger length A1 of the PMOS transistor P1, and the finger length b1of the NMOS transistor N11 is longer than the finger length B1 of theNMOS transistor N1. Meanwhile, the finger length b1 of the NMOStransistor N11 is shorter than the finger length A1 of the PMOStransistor P1. Such relations can be summarized as: a1>A1>b1>B1.

As thus described, in the relation between the I/O section 101 and thelogic circuit section 102, at least in the MOS transistors of the sameconductive type, the finger length of the MOS transistor constitutingthe logic circuit section 102 is made longer than the finger length ofthe MOS transistor constituting the I/O section 101.

It is to be noted that, although the relation between the I/O section101 and the logic circuit section 102 was described above, the same canbe applied to the relations between the I/O section 101 and othercircuits included in the core circuit section.

This is a configuration not seen in the conventional semiconductorintegrated circuit device having the input/output circuit section andthe core circuit section.

B-4. Effect

As thus described, by making the finger length of the MOS transistorconstituting the input/output circuit section shorter than the fingerlength of the MOS transistor in the core circuit section, it is possibleto suppress the substrate floatation effect with certainty even when thecollisional ionization phenomenon apparently occurs at the drain end, soas to prevent deterioration in transistor characteristic caused by thesubstrate floatation effect.

It is to be noted that both in the P-channel type and the N-channeltype, deterioration in transistor characteristic caused by the substratefloatation effect can be prevented.

In addition, although FIG. 4 shows the finger length b1 of the NMOStransistor N11 being shorter than the finger length A1 of the PMOStransistor P1, a case is also contrived where the finger length b1 ofthe NMOS transistor N11 is longer than the finger length of the PMOStransistor P1, or where both finger lengths are the same.

Here, as a specific example of the case where the finger length of eachof the transistors is set so as to establish the relation: a1>b1>A1>B1,the relation: a1 (4 μm)>b1 (2 μm)>A1 (1 μm)>B1 (0.5 μm), can be citedwhen a semi conductor device called 90-nm node is taken as an example.

Further, the both-side potential fixing has been adopted in all the MOStransistor in the constitutional example of the I/O section 101 and thelogic circuit section 102 shown in FIG. 4. When the both-side potentialfixing is adopted, the body resistance of the body region can be madesubstantially half as large as in the case of the one-side potentialfixing, thereby leading to enhancement of the effect of suppressing thesubstrate floatation effect. This means that, in other words, even whenthe finger length having potentials fixed to both sides thereof isdoubled as compared to that of the MOS transistor having a potentialfixed to one side thereof, the same degree of inhibitive power againstthe substrate floatation effect as in the MOS transistor having apotential fixed to one side thereof, and hence adoption of the both-sidepotential fixing allows setting of a longer finger length.

It should be noted that, as shown in FIG. 4, even when the finger lengthof the MOS transistor constituting the I/O section 101 is made shorterthan the finger length of the MOS transistor constituting the logiccircuit section 102, the function of the I/O section 101 would not beimpaired so long as the total finger lengths of the MOS transistors (aplurality of MOS transistors being connected in parallel) is madeequivalent to the gate width the most constituting the I/O section 101is required to have.

C. Second Constitutional Example of Device

Next, a second constitutional example of the I/O section 101 and thelogic circuit section 102 is described using FIG. 5.

C-1. Configuration of I/O Section

In FIG. 5, the I/O section 101 is provided with: a transistor columnwhere a PMOS transistor P21 and an NMOS transistor N21 are provided inparallel in the gate width direction, and the gate electrodes G1 of bothtransistors are connected so as to be a common gate electrode; and atransistor column where a PMOS transistor P22 and an NMOS transistor N22are provided in parallel in the gate width direction, and the gateelectrodes G1 of both transistors are connected so as to be a commongate electrode.

It is to be noted that the basic transistor structures of the PMOStransistor P21 and the NMOS transistor N21 are the same as those of thePMOS transistor P1 and the NMOS transistor N1 which were described usingFIG. 4 and descriptions thereof are thus omitted. Accordingly, each ofthe PMOS transistor P21 and the NMOS transistor N21 has a configurationwhere the two MOS transistors are connected in parallel, but those aretreated as one transistor for the sake of convenience.

The body contact regions 24 and 14 are provided on the outside of bothends of the two gate electrodes G1 in the gate width direction of thePMOS transistor P21 and the NMOS transistor N21, in positions apart fromthe respective active regions. The partial trench isolation insulatingfilm PT is provided between the body contact regions 24 and 14 and therespective active regions of the PMOS transistor P21 and the NMOStransistor N21, and each of the body contact regions 24 and 14 areelectrically connected to the body region through an SOI layer (wellregion) under the partial trench isolation insulating film PT.

Therefore, in the PMOS transistor P21 and the NMOS transistor N21, theone-side potential fixing is adopted which fixes a potential of one endout of both ends of the body region in the gate width direction.

It is to be noted that on the periphery of each of the PMOS transistorP21 and the NMOS transistor N21 except for the portion provided with thepartial trench isolation insulating film, the full trench isolationinsulating film is formed.

Further, each of the PMOS transistor P22 and the NMOS transistor N22 hasfour gate electrodes G1 provided in parallel in the gate lengthdirection, and the PMOS transistor P22 has a configuration where fourPMOS transistors are connected in parallel, but those are treated as onetransistor for the sake of convenience. It should be noted that thebasic transistor structure is the same as that of the PMOS transistorP21 and its description is thus omitted.

Similarly, the NMOS transistor N22 has a configuration where four NMOStransistors are connected in parallel, but those are treated as onetransistor for the sake of convenience. It should be noted that thebasic transistor structure is the same as that of the NMOS transistorN21 and its description is thus omitted.

C-2. Configuration of Logic Circuit Section

Further, the logic circuit section 102 is provided with: a transistorcolumn where a PMOS transistor P31 and an NMOS transistor N31 areprovided in parallel in the gate width direction, and the gateelectrodes G11 of both transistors are connected so as to be a commongate electrode; and a transistor column where a PMOS transistor P32 andan NMOS transistor N32 are provided in parallel in the gate widthdirection, and the gate electrodes G11 of both transistors are connectedso as to be a common gate electrode.

It should be noted that the basic transistor structures of the PMOStransistor P31 and the NMOS transistor N31 are the same as those of thePMOS transistor P11 and the NMOS transistor N11 which were describedusing FIG. 4 and descriptions thereof are thus omitted.

The body contact regions 44 and 34 are provided on the outside of bothends of the two gate electrodes G1 in the PMOS transistor P31 and theNMOS transistor N31 in the gate width direction, in positions apart fromthe respective active regions. The partial trench isolation insulatingfilm PT is provided between the body contact regions 44 and 34 and therespective active regions of the PMOS transistor P31 and the NMOStransistor N31, and each of the body contact regions 44 and 34 areelectrically connected to the body region through the SOI layer (wellregion) under the partial trench isolation insulating film PT.

Therefore, in the PMOS transistor P31 and the NMOS transistor N31, theone-side potential fixing is adopted, which fixes a potential of one endout of both ends of the body region in the gate width direction.

Further, each of the PMOS transistor P32 and the NMOS transistor N32 hastwo gate electrodes G11 provided in parallel in the gate lengthdirection, and the PMOS transistor P32 has a configuration where fourPMOS transistors are connected in parallel, but those are treated as onetransistor for the sake of convenience. It should be noted that thebasic transistor structure is the same as that of the PMOS transistorP31 and its description is thus omitted.

Similarly, the NMOS transistor N32 has a configuration where four NMOStransistors are connected in parallel, but those are treated as onetransistor for the sake of convenience. It should be noted that thebasic transistor structure is the same as that of the NMOS transistorN31 and its description is thus omitted.

C-3. Comparison Between I/O Section and Logic Circuit Section

Next, MOS transistors constituting the I/O section 101 and the logiccircuit section 102 is subjected to comparison with reference to FIG. 5.

First, a focus is placed on the transistor column consisting of the PMOStransistor P21 and the NMOS transistor N21 in the I/O section 101. Thistransistor column is configured such that a finger length A2 of the gateelectrode G1 of the PMOS transistor P21 is made about twice as long as afinger length B2 of the gate electrode G1 of the NMOS transistor N21.This also applies to the PMOS transistor P22 and the NMOS transistorN22.

Here, a focus is placed on the transistor column consisting of the PMOStransistor P31 and the NMOS transistor N31 in the logic circuit section102. This transistor column is configured such that a finger length a2of the gate electrode G11 of the PMOS transistor P31 is made about twiceas long as a finger length b2 of the gate electrode G11 of the NMOStransistor N31. This also applies to the PMOS transistor P32 and theNMOS transistor N32.

Next, a focus is placed on the finger length of each of the PMOStransistor P21 and the NMOS transistor N21 in the I/O section 101 andthe PMOS transistor P31 and the NMOS transistor N31 in the logic circuitsection 102, to find the magnitude relation of these finger lengths asfollows.

Namely, the finger length a2 of the PMOS transistor P31 is longer thanthe finger length A2 of the PMOS transistor P21, and the finger lengthb2 of the NMOS transistor N31 is longer than the finger length B2 of theNMOS transistor N21.

Meanwhile, the finger length b2 of the NMOS transistor N31 is shorterthan the finger length A2 of the PMOS transistor P21. Such a relationcan be summarized as: a2>A2>b2>B2.

As thus described, in the relation between the I/O section 101 and thelogic circuit section 102, at least in the MOS transistors of the sameconductive type, the finger length of the MOS transistor constitutingthe logic circuit section 102 is made longer than the finger length ofthe MOS transistor constituting the I/O section 101, which is the sameas the constitutional example of the input/output circuit section 101and the logic circuit section 102 described using FIG. 4.

However, as described before, the one-side potential fixing has beenadopted in the PMOS transistors P21 and P22 and the NMOS transistors N21and N22 in the input/output circuit section 101 and the S transistor P31and P2 and the NMOS transistors N31 and N32 in the logic circuit section102, and therefore, the finger length of each of the transistors are setshorter than in the case of adopting the both-side potential fixing.

In addition, although FIG. 5 shows the finger length b2 of the NMOStransistor N31 being shorter than the finger length A2 of the PMOStransistor P21, a case is also contrived where the finger length b2 ofthe NMOS transistor N31 is longer than the finger length of the PMOStransistor P21, or where both finger lengths are the same.

Here, as a specific example of the case where the finger length of eachof the transistors is set so as to establish the relation: a2>b2>A2>B2,the relation: a2 (2 μm)>b2 (1 μm)>A2 (0.5 μm)>B2 (0.25 μm), can be citedwhen the semi conductor device called 90-nm node is taken as an example.

It is to be noted that, although the relation between the I/O section101 and the logic circuit section 102 was described above, the same canbe applied to the relations between the I/O section 101 and othercircuits included in the core circuit section.

C-4. Effect

As thus described, by making the finger length of the MOS transistorconstituting the input/output circuit section shorter than the fingerlength of the MOS transistor in the core circuit section, it is possibleto suppress the substrate floatation effect with certainty even when thecollisional ionization phenomenon apparently occurs at the drain end, soas to prevent deterioration in transistor characteristic caused by thesubstrate floatation effect. This applies to both the P-channel type andthe N-channel type.

It is to be noted that, although adoption of the MOS transistor having apotential fixed to one side thereof requires setting of the fingerlength of each transistor to be shorter than in the case of adoption ofthe MOS transistor having potentials fixed to both sides thereof, theMOS transistor can be structurally simplified as compared to the MOStransistor having potentials fixed to both sides thereof, since only alimited portion is necessary as a region for forming the partial trenchisolation insulating film. Hence an area efficiency of the MOStransistor can be enhanced, thereby allowing an increased packingdensity.

Moreover, when the partial trench isolation insulating film is formed soas to surround the drain region and the source region, a PN junction isformed at a contact portion between the SOI layer under the partialtrench isolation insulating film and the drain region and/or the sourceregion. A performance characteristic of the MOS transistor may beaffected if junction leakage occurs at the PN junction portion, andthere hence is an advantage in adopting the one-side potential fixing inthat only a small region for forming the partial trench isolationinsulating film is necessary.

D. Third Constitutional Example of Device

Next, a third constitutional example of the I/O section 101 and thelogic circuit section 102 is described using FIG. 6.

D-1. Configuration of I/O Section

In FIG. 6, the I/O section 101 is provided with: a transistor columnwhere a PMOS transistor P21 and an NMOS transistor N21 are provided inparallel in the gate width direction, and the gate electrodes G1 of bothtransistors are connected so as to be a common gate electrode; and atransistor column where a PMOS transistor P41 and an NMOS transistor N41are provided in parallel in the gate width direction, and the gateelectrodes G2 of both transistors are connected so as to be a commongate electrode.

Here, the PMOS transistor P21 and the NMOS transistor N21 are the sameas those described using FIG. 5, and descriptions thereof are thusomitted.

The number of gate electrodes G2 in common between the PMOS transistorP41 and the NMOS transistor N41 is one, and in the PMOS transistor P41,a source region 62 and a drain region 63 in which the P-type impuritieshave been introduced are provided on the outside of both side surfacesof the gate electrode G2 in the gate length direction within the surfaceof the SOI substrate SB.

Similarly, in the NMOS transistor N41, a source region 52 and a drainregion 53 in which the N-type impurities have been introduced areprovided on the outside of both side surfaces of the gate electrode G2in the gate length direction within the surface of the SOI substrate SB.

In the PMOS transistor P41, the periphery of the source region 62 issurrounded by the partial trench isolation insulating film PT, and thepartial trench isolation insulating film PT is provided so as to be incontact with both side surfaces of the drain region 63 in the gate widthdirection.

Similarly, in the NMOS transistor N41, the periphery of the sourceregion 52 is surrounded by the partial trench isolation insulating filmPT, and the partial trench isolation insulating film PT is provided soas to be in contact with both side surfaces of the drain region 53 inthe gate width direction.

The partial trench isolation insulating film PT surrounding the sourceregion 62 of the PMOS transistor P41 is provided such that part thereofreaches a body contact region 24 provided on the outside of the end ofthe gate electrode G1 in the gate width direction of the PMOS transistorP21.

Further, the partial trench isolation insulating film PT surrounding thesource region 52 of the NMOS transistor N41 is provided such that partthereof reaches a body contact region 14 provided on the outside of theend of the gate electrode G1 in the gate width direction of the NMOStransistor N21.

Adoption of such a configuration allows fixing of a potential of eachend of the body region in the gate width direction in each of the PMOStransistor P41 and the NMOS transistor N41, thereby making bodyresistance of the body region substantially half as large as in the caseof the one-side potential fixing, so that the effect of suppressing thesubstrate floatation effect is increased.

It is therefore possible to make the finger length of the PMOStransistor P41 and the NMOS transistor N41 longer than that of the PMOStransistor P21 and the NMOS transistor N21 which have a potential fixedto one side thereof.

D-2. Configuration of Logic Circuit Section

In FIG. 6, the logic circuit section 102 is provided with: a transistorcolumn where a PMOS transistor P32 and an NMOS transistor N32 areprovided in parallel in the gate width direction, and the gateelectrodes G11 of both transistors are connected so as to be a commongate electrode; and a transistor column where a PMOS transistor P51 andan NMOS transistor N51 are provided in parallel in the gate widthdirection, and the gate electrodes G12 of both transistors are connectedso as to be a common gate electrode.

Here, the PMOS transistor P32 and the NMOS transistor N32 are the sameas those described using FIG. 5, and descriptions thereof are thusomitted.

The number of gate electrodes G12 in common between the PMOS transistorP51 and the NMOS transistor N51 is one, and in the PMOS transistor P51,a source region 82 and a drain region 83 in which the P-type impuritieshave been introduced are provided on the outside of both side surfacesof the gate electrode G2 in the gate length direction within the surfaceof the SOI substrate SB.

Similarly, in the NMOS transistor N51, a source region 72 and a drainregion 73 in which the N-type impurities have been introduced areprovided on the outside of both side surfaces of the gate electrode G12in the gate length direction within the surface of the SOI substrate SB.

In the PMOS transistor P51, the periphery of the source region 82 issurrounded by the partial trench isolation insulating film PT, and thepartial trench isolation insulating film PT is provided so as to be incontact with both side surfaces of the drain region 83 in the gate widthdirection.

Similarly, in the NMOS transistor N51, the periphery of the sourceregion 72 is surrounded by the partial trench isolation insulating filmPT, and the partial trench isolation insulating film PT is provided soas to be in contact with both side surfaces of the drain region 73 inthe gate width direction.

The partial trench isolation insulating film PT surrounding the sourceregion 82 of the PMOS transistor P51 is provided such that part thereofreaches a body contact region 44 provided on the outside of the end ofthe gate electrode G11 in the gate width direction of the PMOStransistor P32.

The partial trench isolation insulating film PT surrounding the sourceregion 72 of the NMOS transistor N51 is provided such that part thereofreaches a body contact region 34 provided on the outside of the end ofthe gate electrode G11 in the gate width direction of the NMOStransistor N32.

Adoption of such a configuration allows fixing of a potential of eachend of the body region in each of the PMOS transistor P51 and the NMOStransistor N51, thereby making the body resistance of the body regionsubstantially half as large in the gate width direction as in the caseof fixing of the body region, so that the effect of suppressing thesubstrate floatation effect is increased.

It is therefore possible to make the finger length of the PMOStransistor P51 and the NMOS transistor N51 longer than that of the PMOStransistor P32 and the NMOS transistor N32 which have a potential fixedto one side thereof.

D-3. Comparison Between I/O Section and Logic Circuit Section

Next, MOS transistors constituting the I/O section 101 and the logiccircuit section 102 is subjected to comparison with reference to FIG. 6.

The I/O section 101 is provided with the PMOS transistor P41 and theNMOS transistor N41 which have potentials fixed to both sides thereof,and the PMOS transistor P21 and the NMOS transistor N21 which have apotential fixed to one side thereof.

As described above, the finger length of the MOS transistor havingpotentials fixed to both sides thereof can be made longer than that ofthe MOS transistor having a potential fixed to one side thereof. Afinger length A3 of the gate electrode G2 of the PMOS transistor P41 anda finger length B3 of the gate electrode G2 of the NMOS transistor N41are configured to be about twice as long as the finger length A2 of thegate electrode G1 of the PMOS transistor P21 and the finger length B2 ofthe gate electrode G1 of the NMOS transistor N21.

The logic circuit section 102 comprises the PMOS transistor P51 and theNMOS transistor N51 which have potentials fixed to both sides thereofand the PMOS transistor P32 and the NMOS transistor N32 which have apotential fixed to one side thereof. A finger length a3 of the gateelectrode G12 of the PMOS transistor P51 and a finger length b3 of thegate electrode G12 of the NMOS transistor N51 are configured to be abouttwice as long as the finger length a2 of the gate electrode G11 of thePMOS transistor P32 and the finger length b2 of the gate electrode G11of the NMOS transistor N32.

Next, a focus is placed on the finger length of each of the PMOStransistor P21, the NMOS transistor N21, the PMOS transistor P41 and theNMOS transistor N41 in the I/O section 101, and the PMOS transistor P32,the NMOS transistor N32, the PMOS transistor P51 and the NMOS transistorN51 in the logic circuit section 102, to find the magnitude relation ofthese finger lengths as follows.

Namely, the finger length a2 of the PMOS transistor P32 is longer thanthe finger length A2 of the PMOS transistor P21, and the finger lengthb2 of the NMOS transistor N32 is longer than the finger length B2 of theNMOS transistor N21.

Meanwhile, the finger length b2 of the NMOS transistor N32 is shorterthan the finger length A2 of the PMOS transistor P21. Such a relationcan be summarized as: a2>A2>b2>B2.

Further, the finger length a3 of the PMOS transistor P51 is longer thanthe finger length A3 of the PMOS transistor P41, and the finger lengthb3 of the NMOS transistor N51 is longer than the finger length B3 of theNMOS transistor N41.

Meanwhile, the finger length b3 of the NMOS transistor N51 is shorterthan the finger length A3 of the PMOS transistor P41. Such a relationcan be summarized as: a3>A3>b3>B3.

As thus described, the relation between the I/O section 101 and thelogic circuit section 102 is the same as in the constitutional exampleof the I/O section 101 and the logic circuit section 102 which wasdescribed using FIG. 4 in that at least in the MOS transistors of thesame conductive type, the finger length of the MOS transistorconstituting the logic circuit section 102 is set so as to be longerthan the finger length of the MOS transistor constituting the I/Osection 101.

However, as described before, since the finger length of the MOStransistor having potentials fixed to both sides thereof can be madelonger than that of the MOS transistor having a potential fixed to oneside thereof, even when the transistors are of the same conductive type,the finger length of the PMOS transistor P41 having potentials fixed toboth sides thereof is longer than that of the PMOS transistor P32 havinga potential fixed to one side thereof.

The finger length of the MOS transistor constituting the I/O section 101may be longer than that of the logic circuit section 102 if systems forfixing a potential are different between the two MOS transistors even ofthe same conductive type. However, as described above, when theconductive types as well as the potential fixing systems are the samebetween the two MOS transistor, the finger length of the MOS transistorconstituting the logic circuit section 102 is set so as to be longerthan the finger length of the MOS transistor constituting the I/Osection 101.

It is to be noted that, although the relation between the I/O section101 and the logic circuit section 102 was described above, the same canbe applied to the relations between the I/O section 101 and othercircuits included in the core circuit section.

In addition, in the MOS transistors constituting the I/O section 101 andthe logic circuit section 102 shown in FIG. 6, the NMOS transistor N21of the I/O section 101 and the NMOS transistor N32 in the logic circuitsection 102 were shown as the MOS transistors having a potential fixedto one side thereof, but those NMOS transistors may be made ones havingpotentials fixed to both sides thereof since the substrate floatationeffect is apt to occur in an NMOS transistor.

D-4. Effect

As thus described, by making the finger length of the MOS transistorconstituting the input/output circuit section shorter than the fingerlength of the MOS transistor in the core circuit section, it is possibleto suppress the substrate floatation effect with certainty even when thecollisional ionization phenomenon apparently occurs at the drain end, soas to prevent deterioration in transistor characteristic caused by thesubstrate floatation effect. This applies to both the P-channel type andthe N-channel type.

It is to be noted that in the case of mixed mounting of both the MOStransistor having a potential fixed to one side thereof and the MOStransistor having potentials fixed to both sides thereof, as for theNMOS transistors of the same conductive type with potentials fixed inthe same system, it is possible to obtain the above effect by settingthe finger length of the NMOS transistor constituting the logic circuitsection 102 so as to be longer than the finger length of the MOStransistor constituting the I/O section 101.

This can be translated into as follows. In this case, the input/outputcircuit section and the core circuit section have a plurality of kindsof MOS transistors with different finger lengths, and the maximum fingerlength among the finger lengths of the plurality of kinds of MOStransistors in the input/output circuit section is shorter than themaximum finger length among the finger lengths of the plurality of kindsof MOS transistors in the core circuit section, which allows preventionof deterioration in transistor characteristic caused by the substratefloatation effect.

E. Modified Example

In the above embodiments according to the present invention, thesemiconductor integrated circuit device was configured on the SOIsubstrate, and it was described that a crystal orientation and a crystalplane orientation of the SOI layer area are identical over the SOIsubstrate surface and that the finger length of the PMOS transistor isbasically set to twice as long as that of the NMOS transistor.

This is due to a current driving capacity of the PMOS transistor beingabout half as large as that of the NMOS transistor. However, recently, atechnique for producing an SOI substrate with its crystal orientation orcrystal plane orientation partially changed has been disclosed.

For example, in “High Performance CMOS Fabricated on Hybrid SubstrateWith Different Crystal Orientations” (M. Yang et al., IEDM 2003, pp.453-456), a crystal plane orientation of an SOI layer in a regionforming a PMOS transistor is set to a (110) plane, and a crystal planeorientation of the SOI layer in a region forming a PMOS transistor isset to a (100) plane, to set a channel direction of the PMOS transistorto a <110> direction and a channel direction of the NMOS transistor to a<100> direction.

Adoption of this configuration enables enhancement in current drivingpower of the PMOS transistor, so as to set the finger length of the PMOStransistor to two-thirds of the finger length of the NMOS transistor.

FIG. 7 shows a sectional view in the gate width direction in the case offorming a PMOS transistor P10 on the SOI layer 3 a having the (110)plane and an NMOS transistor N20 on the SOI layer 3 having the (100)plane.

As shown in FIG. 7, a configuration is made such that the buried oxidefilm 2 and the SOI layer 3 are sequentially formed on the siliconsubstrate 1, and part of the SOI layer 3 has the (110) plane as the SOIlayer 3 a.

Since the direction perpendicular to the paper surface is the crystalorientation <100> in the SOI layer 3 and the direction perpendicular tothe paper surface is the crystal orientation <110> in the SOI layer 3 a,the channel direction of the NMOS transistor N20 is the <100> directionand the channel direction of the PMOS transistor P10 is the <110>direction.

The finger length of the gate electrode G10 of the PMOS transistor P10is configured to be about two-thirds as long as that of the gateelectrode G10 of the PMOS transistor P10.

It should be noted that the gate insulating film GX is provided betweenthe gate electrode G10 and the SOI layer 3 a, and the gate electrode G20and the SOI layer 3.

Further, a configuration is made such that the interlayer insulatingfilm 4 is provided so as to cover the surface of the SOI substrate SBincluding the gate electrodes G10 and G20, and the wiring layer WR isprovided on the interlayer insulating film 4 to be brought into contactwith the contact portion CH.

Since adoption of the configuration as described above leads to settingof the finger length of the PMOS transistor to two-thirds as long asthat of the NMOS transistor, the finger length of the PMOS transistormay be set to two-thirds as long as that of the NMOS transistor withinthe same circuit section when the two MOS transistor have potentialsfixed in the same system. Hence, the configuration is not limited to oneas shown in FIG. 4, for example, where the finger length of the gateelectrode G1 of the PMOS transistor P1 is about twice as long as thefinger length of the gate electrode G1 of the NMOS transistor N1.

Further, although the semiconductor integrated circuit device isconfigured on the SOI substrate in the embodiments according to thepresent invention as thus described, for example in Japanese PatentApplication Laid-Open No. 1996-213562, a semiconductor device isproposed, which comprises an SOI substrate region and a bulk substrateregion and in which an input/output circuit is formed in the bulksubstrate region while an internal circuit is formed in the SOIsubstrate region.

When such a configuration is adopted, it is preferable that the fingerlength of the MOS transistor constituting the circuit section formed inthe bulk substrate region be set so as to avoid restriction on area, andthe restriction on finger length according to the present invention beapplied to the circuit section formed in the SOI substrate region.

While the invention has been shown and described in detail, theforegoing description is in all aspects illustrative and notrestrictive. It is therefore understood that numerous modifications andvariations can be devised without departing from the scope of theinvention.

1. A semiconductor integrated circuit device, provided on an SOI substrate and comprising: an input/output circuit section; and a core circuit section, which is provided more internally than said input/output circuit section and operate at a lower power supply voltage than said input/output circuit section, wherein said input/output circuit section has a first MOS transistor of a first conductivity type, said core circuit section has a second MOS transistor of said first conductivity type, and a first finger length of a first gate electrode of said first MOS transistor, which is defined by a length of a portion on an active region, is set shorter than a second finger length of a second gate electrode of said second MOS transistor, which is defined by a length of a portion on an active region.
 2. The semiconductor integrated circuit device according to claim 1, wherein said first conductivity type is P type.
 3. The semiconductor integrated circuit device according to claim 1, wherein said first conductivity type is N type.
 4. The semiconductor integrated circuit device according to claim 1, wherein said input/output circuit section has a third MOS transistor of a second conductivity type, said core circuit section has a fourth MOS transistor of said second conductivity type, and a third finger length of a third gate electrode of said third MOS transistor in said input/output circuit section, which is defined by a length of a portion on an active region, is set shorter than a fourth finger length of a fourth gate electrode of said fourth MOS transistor in said core circuit section, which is defined by a length of a portion on an active region.
 5. The semiconductor integrated circuit device according to claim 4, wherein in said input/output circuit section, said third finger length of said third MOS transistor is set shorter than said first finger length of said first MOS transistor, and in said core circuit section, said fourth finger length of said fourth MOS transistor is set shorter than said second finger length of said second MOS transistor.
 6. The semiconductor integrated circuit device according to claim 5, wherein said first conductivity type is P type, and said second conductivity type is N type.
 7. The semiconductor integrated circuit device according to claim 1, wherein, in said input/output circuit section and said core circuit section, said first and second MOS transistors include transistors having potentials fixed to both sides thereof, where body regions under said first and second gate electrodes are electrically connected to body contact regions provided on the outside of both ends of said first and second gate electrodes in a gate width direction within the surface of said SOI substrate.
 8. The semiconductor integrated circuit device according to claim 1, wherein, in said input/output circuit section and said core circuit section, said first and second MOS transistors include transistors having a potential fixed to one side thereof, where a body region under said first gate electrode is electrically connected to body contact regions provided on the outside of one ends of said first and second gate electrodes in the gate width direction within the surface of said SOI substrate.
 9. A semiconductor integrated circuit device, provided on an SOI substrate and comprising: an input/output circuit section; and a core circuit section, which is arranged more internally than said input/output circuit section and operates at a lower power-supply voltage than said input/output circuit section, wherein said input/output circuit section has a plurality of kinds of MOS transistors in a first group, said core circuit section has a plurality of kinds of MOS transistors in a second group, a finger length of each of gate electrodes of the plurality of kinds of MOS transistors in said first group in said input/output circuit section is different, the length being defined by a length of a portion on an active region, a finger length of each of gate electrodes of the plurality of kinds of MOS transistors in said second group in said core circuit section is different, the length being defined by a length of a portion on an active region, and the maximum finger length among the respective finger lengths of the plurality of kinds of MOS transistors in said first group is shorter than the maximum finger length among the respective finger lengths of the plurality of kinds of MOS transistors in said second group.
 10. The semiconductor integrated circuit device according to claim 9, wherein, in said input/output circuit section and said core circuit section, the plurality of kinds of MOS transistors in said first group and said second group includes: transistors having potentials fixed to both sides thereof, where body regions under said respective gate electrodes are electrically connected to body contact regions provided on the outside of both ends of said gate electrodes in the gate width direction within the surface of said SOI substrate; and transistors having a potential fixed to one side thereof, where body regions under said respective gate electrode are electrically connected to body contact regions provided on the outside of one ends of said gate electrodes in the gate width direction within the surface of said SOI substrate. 